Guys dont..... Do that... I mean sane guys...
I have A LOT of kinky friends amd they dont do that. We joke around a lot about these topics, mainly because we dont judge eachother so were very frank, but still i have never heard of anyone who came to a girl and asked her if she wants to see his pee-pee. It reminds me of kids in kindergarten or something... O_o
But hey if thats your choice and if you dont have a boyfriend go ahead... I mean if you do i wouldnt recommend it since its the same if a chick would ask a guy in a relationship does he wants to see her tits and then the guys gf finds out. That would be a disaster...
But yeah, your preference, your life, your choice...
Just stay safe. If hes physically stronger than you i wouldnt recommend it since the guy is maybe kinky or a hidden dexter or a rapist, i dont know him. But all people have secrets...